In a wireless communications system such as a long term evolution (Long Term Evolution, LTE) system or a long term evolution advanced (Long Term Evolution Advanced, LTE-Advanced) system, a downlink multiple access mode generally is an orthogonal frequency division multiple access (Orthogonal Frequency Division Multiple Access, OFDMA) mode. Downlink resources of a system are divided into a plurality of orthogonal frequency division multiplexing (Orthogonal Frequency Division Multiplexing, OFDM) symbols from the perspective of time. The downlink resources of the system are also divided into a plurality of subcarriers from the perspective of frequency. In the LTE system, a complete physical downlink control channel (Physical Downlink Control Channel, PDCCH) may be mapped to one or several control channel elements (Control Channel Element, CCE). According to LTE Release 8/9/10, a PDCCH may be mapped to 1 (one), 2 (two), 4 (four), or 8 (eight) CCEs, that is, a PDCCH is formed from the 1, 2, 4, or 8 CCEs, which respectively corresponds to an aggregation level 1, 2, 4, or 8 of the PDCCH. Furthermore, each CCE is formed from 9 (nine) resource element groups (Resource Element Group, REG), and a REG occupies 4 (four) resource elements (Resource Element, RE).
In the LTE or LTE-Advanced system, a physical downlink control channel (Physical Downlink Control Channel, PDCCH) transmitted based on a manner of precoding is introduced, that is, an enhanced physical downlink control channel (Enhanced Physical Downlink Control Channel, ePDCCH). The ePDCCH allows that a user equipment (User Equipment, UE) is capable of carrying out demodulation based on specific reference signals, that is, the demodulation reference signals (Demodulation Reference Signal, DMRS). The ePDCCH is transmitted in a region for transmitting a downlink data channel in a subframe, and frequency division can be performed for it and a physical downlink shared channel (Physical Downlink Shared Channel, PDSCH). A base station may send the ePDCCH on a unit physical resource block (Physical Resource Block, PRB) with a good channel condition according to a channel status reported by a terminal. REs forming each PRB can be divided into multiple enhanced resource element groups (Enhanced Resource Element Group, eREG), and each eREG includes a specified number of REs.
In the conventional art, although the ePDCCH is introduced and a manner of generating an eREG on a PRB is provided, a manner of generating an enhanced control channel element (Enhanced Control Channel Element, eCCE) according to an eREG so as to transmit an enhanced control channel such as an ePDCCH through the eCCE is blank in the conventional art.